The purpose of this work is to explore in depth the nature of the sweet taste receptor site in mammals. This sweet taste receptor site, located on the taste receptor cell membrane, will be studied indirectly by recording the electrophysiological response taken from the whole chorda tympani nerve of the Mongolian Gerbil. The first experiments will involve a specificity study investigating the gerbil's response to a variety of sugar and saccharin derivatives. The purpose of the second group of experiments will be to determine the number of receptor sites which are responsible for the sweetener taste responses. This will be accomplished using inhibition, neural adaptation and mixtures. With regard to inhibition experiments, we intend to examine the effect of gymnemic acid, mercuric chloride, non-stimulating sweetener derivatives, and photo-affinity compounds. In a further attempt to elucidate the number of receptor sites, cross-adaptation and mixture experiments will be conducted. While most electrophysiological recordings, including those of the experiments listed above, are taken from the whole chorda tympani nerve, since it is more easily accessible, it would be highly desirable to pinpoint the response of a single neuron. Therefore, an attempt will be made to repeat the above experiments using this more difficult method. The results of these experiments may eventually be utilized by biochemists in isolating the elusive receptor site.